Flexible electrical resistor and method of manufacturing the same



March 31, 1936. J. J, MUCHER n 2,035,911

FLEXIBLE ELECTRICAL RESISTOR AND METHOD 0F' MANUFACTURING THE SAME FiledJan. lO, 1955 INVENTOR, JOHN J. Mac/ign {Mfw ATTORNEYS Patented Mar. 31,T936 yUNITED STATES FLEXIBLE ELECTRICAL RESISTOR AND METHOD 0FMANUFACTURING THE SAME John J. Mucher, Brooklyn, N. Y.

Application January 10, 1935, Serial No. 1,167

6 Claims.

This invention relates to flexible electrical resistors of the typehaving a fixed ohmage or'resistance value and refers more particularlyto an improved construction of a resistor of this character and a.method of manufacturing the same.

Resistors of this character, particularly for use in connection withradio receiving apparatus, should possess a fixed or constant resistancevalue and to this end, the invention provides a resistor and method ofmanufacturing the same so that the ohmage or resistance value of theresistor may be accurately predetermined, fixed and maintained.

The invention comprehends an improved exible electrical resistor whichis so constructed that its ohmage or predetermined 'resistance valueremains constant when the resistor is subjected to flexing strains orstresses encounteredwhen the resistor is bent or looped.

More particularly the invention resides in an improved exible electricalresistor which includes a lcore of insulating material having aresistance wire Wound thereon and a pair of tubular terminal members atits opposite ends each of which is formed with an outer end adapted toabut with the outer end of the core and adapted to telescopically litover the core and winding. with a braided insulating sleeve for thecovering, the convolutions of the resistor wire located between theinner ends of said members and which sleeve is initially contractedlongitudinally so that it possesses an inherent tendency to expandlongitudinallyl for covering and maintaining the convolutions betweenthe inner ends of the applied terminal members in constantly 'coveredcondition. y

Due to the fact that the improved resistor embodies a winding ofextremely fine wire as fine as .001 to .0015 of an inch, it isimpossible to strip off the usual insulation covering without destroyingthe winding and .hence the present invention comprehends a method ofmanufacturing flexible electrical resistors whichfincludesthe braidingof an insulation covering over a core wound with a. resistance wire asfine as .001 to .0015 of an "inch, the cutting of the assemblage thusformed into predetermined lengths, the application to the opposite endsthereof of tubular terminal members of a size to push back the braidedcovering so as to expose the endmost convolutions of the winding withoutbreaking, distorting or otherwise disturbing'the same, while theterminal members receive therein the ends lof the core and the endconvolutions of the winding exposed by the (Cl. 24H-67) pushing back ofthe covering for establishing' electrical connection between theterminals and. winding. By this method, the resistance value or ohmageof the resistor may be predetermined as the same is fixed by the lengthof the winding between the inner ends of the terminals. The method alsoinsures firm electrical connection between the winding and the terminalswhile avoiding any. cutting or fraying of the wire which takes placewhen an attempt is made to sever the insulation covering for the purposeof stripping off the end portions of the covering. The resistors of thistype are subjected to severe man ufacturing tests and when constructedby the foregoing method, the number of rejections for failure to meetthe requirements ofthe tests are materially lessened.

Further objects of the invention reside in a method of manufacturingresistors of the indicated character which greatly simplifles themanufacture thereof, reduces the expense of production and increases thequality and character of the product.

With the above enumerated and other objects in view, reference is nowmade to the following specification and accompanying drawing in whichthere has been set, forth one embodiment of the invention, while theappended claims cover variations and modifications which fall Within thespirit and scope of the invention.

In the drawing:

Fig. 1 is a fragmentary side view partially in the winding and core withthe braided covering cut to a length for predetermining the ohmage orresistance value of the resistor when completed.

Fig. 4 is a view similar to Fig. 3 illustrating the terminal members inpartially applied position and demonstrating the manner of theirapplica# tion.

Fig. 5 is a similar sectional viewA through the resistor showing theterminal members, in fully applied position. y

Fig. 6 is a side elevation partially in section of the completedresisto; constructed in accordance with the invention and produced inaccordance with the improved method.

The method of manufacturing a flexible electrical resistor of the typespeciiied and constructspirally winding a resistance wine i of extremelysmall'diameter, as fine as .001 'to .0015 of an inch, continuouslyaround an insulating core il,

/which core is of such a character that the convolutions aresubstantially equally spaced s and partially embedded in the peripherythereof so as to insulate adjacent convolutlons-from each other when theresistor is bent, flexed or otherwise distorted from a straight line.The resistance wire and core thus produced is then continuously cov-sered by a braided covering I2 which isimpreg- I resistor so as to coverand maintain the connated with a suitable coating such as lacquer,varnish, wax'or the like. The product thus produced may be suitablyspooled and stored vaway in quantities for future use to be incorporatedin resistors of various sizes and values. The resistance wire and itscore and braided covering are made into thenished resistors by 4cuttingthe same into predetermined lengths as shown in Fig. 3 of the drawingand. the length of the severed sections serves as an accurate gage orthe resistance value or ohmage of the ultimate completed resistor. Y

Tubular terminal members I3 having an outer end 14, are thenl appliedto-the opposite ends of the cut lengths or severed sections bytelescopically engaging the same thereover as shown in Fig. 4 of thedrawing. The members i3 are of a cross sectional size orv diameter toreceive the winding and core, but not of a cross sectional size ordiameter to accommodate the braided cover I2. It, therefore, followsthat the inner ends I5 of the terminal members I3 function to push backthe opposite ends of the braided cover=I ing I2 thereby exposing theendmost convolutions of the cut length or severed sections so thatthesaid exposed convolutions of the resistance wire I0 are adapted forelectrical connection with the terminal members. After the terminalmembers 'I3 are shoved home, as shown in Fig. 5, the outer ends I4 limitthe inward movement of said terminal members, the terminal members arecompressed and contracted inwardly about the core andwinding, as shownin Fig. 6, as set forth in United States Letters Patent', No. 1,987,489,granted to me January 8, 1935, so that the terminal member` is securelybonded to the winding and core thereby completing the manufacture of theresistor. 4 It will be observed during the telescopic inward movement ofthe terminal members I3 over the winding and core, that the braidedcovering I2 is longitudinally contracted so that it then possesses aninherent tendency to expand longitu` 'dlnally whereby its oppositepushed-back ends iii-e forced into intimate engagement with the innerends I5 ofthe members I3 and by virtue oia.

.this inherent longitudinal expansive action, said? braided coveringwill remain-in said intimate e'n gagement throughout the length of lifeAof the volutions of the resistance wire III between the inner ends ofthe appliedv terminal members in crow sectional size greater than thatoi' the member I3 and of a size to freely iit over and accommodate thebraided covering I2 to lend to the resistor a heat andnishedsweatshirt,l

. stant engagement with ved in accordance with the inventiomconsists inThe nnished resistor manufactured in accordancel with the improvedmethod differs from the ordinary resistors of this type previouslydevised, in that the braided covering I2 in accordance with the presentinvention is initially braid- 5 ed onto the resistance wire and its coreand is. not telescopically itted thereover after the covering has beenmanufactured and cut to lengths. This avoids the loose tting outercoverings and the unsatisfactory and. tedious task of te1escopi iolcally sliding the cut lengths of outer coverings Iover the resistancewire wound on the core which e longitudinal contraction is constantlyunder tension to maintain its opposite pushed-back ends in engagementwith the inner end I5 of the terminal member i3.

What I claim is:

l. A iiexible electrical resistor including anelongated resistanceelement, a tubular terminal member secured over each of the oppositeends oi said resistance element, and a longitudinally contracted tubularcovering formed over, the said resistance element and inherentlyexpansible longitudinally to maintain its opposite endsin constantengagement with the inner ends oi the terminal members.

2. A flexible electrical resistor including a core of insulationmaterial, a resistance wire spirally wound thereon, a tubular terminalmember having an outer portion secured over each of the opposite endsofthe core and the opposite end convolutionsoi the resistance wire andhaving an enlarged inner portion dening a shoulder at its juncture withthe outer portion thereof, and 40 a braided tubular covering surroundingthe core and extending from the shoulder of one terminal member to theshoulder of the other, said covering being initially contractedlongitudinally and placed under tension so as to be inherentlyexpansible longitudinally for maintaining its opposite ends in constantengagement with the shoulders of the terminal members.

3. A method of manufacturing exible electrical resistors including thesteps of braiding anouter protective covering over an elongated re'vsistance element, cutting said covered resistance element together. withthe covering into predetermined lengths and telescopically slidinginwardly over the opposite ends of the said resistance element, tubularterminal members oi' such across sectional size that the inner ends ofsaid members push back the outer covering from said resistance elementand maintain the same under` tension so as to .be inherently expansiblelimsi-160v tudinauy -ior retaining its opposite ends in ontire innerends oi the terminal members.

'4. A'method of manufacturing ilexible electrical resistors includingthe steps of braiding an outer protective covering over a resistancewire spirally wound on a core of insulation material, cutting saidcovered resistance wire and its core together with the covering intopredetermined lengths, telescopically sliding, inwardly over the i"opposite ends of the core and resistance wire of said lengths,tubularterminalv members oi' such a cross sectional size that the innerends of said members push back the outer covering from said. resistancewire and its core and maintainths 76 covering under tension so that thesame is inherently expansible longitudinally for retaining its oppositeends in constant engagement with the inner ends of the terminal members,and bonding the4 terminal members to the opposite ends of the core andthe end convolutions of the wire which are exposed by the pushing backof the outer covering.

5. In a method of making resistors containing two metallic terminalterrines each having an interm'ediate shoulder therein, the steps ofinsertinginto said ferrulesthe opposite end portions of a wired corecovered along the length thereof with acompressible sleeve, bringing theends of the sleeves into abutment with the shoulders.

forcing the ends of the core farther into the ferrules whereby the saidYshoulders compressibly hold back the sleeve against further movement toexpose the coils on the end portions o f. the core, and compressingtogether the ferrules at the shoulders thereof and the adjacent portionsof the exposed coils to establish an electrical connection between saidshoulders through the cov ered winding on the core therebetween.

6. In a method of making resistors containing at each end a metallicterminal ferrule having an intermediate shoulder positioned between anenlarged socket and a constricted tubular portion communicatingtherewith, the steps of inserting into each of said ferrules the endportion of a wired core covered along the length thereof with acompressible sleeve, bringing the ends of each sleeve into abutment withsaid shoulders, forcing the cores into said constricted portions apredetermined distance whereby said shoulders compressibly hold back thesleeves against further movement to cause the compressed end portions ofthe sleeves to remain within said sockets and expose the coils on theend portions of the core to the walls ofthe constricted portions, andcompressing together the ferrules at the shoulders thereof and theadjacent portions of the exposed coils.

JOHN J. MUCHER.

